LRRK2 is a 286 kDa protein in the ROCO protein family with a complex multidomain structure. Protein motifs that have been established for LRRK2 include an armadillo-like (ARM) domain, an ankyrin-like (ANK) domain, a leucine-rich repeat (LRR) domain, a Ras (renin-angiotensin system) of complex (ROC) domain, a C-terminal of ROC (COR) domain, a kinase domain, and a C-terminal WD40 domain. The ROC domain binds guanosine triphosphate (GTP) and the COR domain may be a regulator of the ROC domain's GTPase activity. The kinase domain has structural homology to the MAP kinase kinase kinases (MAPKKK) and has been shown to phosphorylate a number of cellular proteins in vitro, but the endogenous substrate has yet to be determined. LRRK2 has been found in various regions of the brain as well as in a number of peripheral tissues including heart, lung, spleen, and kidney.
LRRK2 has the ability to potentially play a complex role in multiple cellular processes as a consequence of its multi-domain construct, each associated with putative protein-protein interactions, guanosine triphosphatase (GTPase) activity, and kinase activity. For example, LRRK2 has been associated with NFAT inhibition in the immune system and has been linked to vesicle trafficking, presynaptic homeostasis, mammalian target of rapamycin (mTOR) signaling, signaling through the receptor tyrosine kinase MET in papillary renal and thyroid carcinomas, cytoskeletal dynamics, the mitogen-activated protein kinase (MAPK) pathway, the tumor necrosis factor-α (TNF-α) pathway, the Wnt pathway and autophagy. Recent genome-wide association (GWA) genetic studies have implicated LRRK2 in the pathogenesis of various human diseases such as PD, inflammatory bowel disease (Crohn's disease), cancer and leprosy (Lewis, P. A. and Manzoni, C. Science Signaling 2012, 5(207), pe 2).
Parkinson's disease (PD) is a relatively common age-related neurodegenerative disorder resulting from the progressive loss of dopamine-producing neurons and which affects up to 4% of the population over age 80. PD is characterized by both motor symptoms, such as tremor at rest, rigidity, akinesia and postural instability as well as non-motor symptoms such as impairment of cognition, sleep and sense of smell. GWA studies have linked LRRK2 to PD and many patients with point mutations in LRRK2 present symptoms that are indistinguishable from those with idiopathic PD. Over 20 LRRK2 mutations have been associated with autosomal-dominant parkinsonism, and the R1441C, R1441G, R1441H, Y1699C, G2019S, 12020T and N1437H missense mutations are considered to be pathogenic. The LRRK2 R1441G mutation has been shown to increase the release of proinflammatory cytokines (higher levels of TNF-α, IL-1β, IL-12 and lower levels of IL-10) in microglial cells from transgenic mice and thus may result in direct toxicity to neurons (Gillardon, F. et al. Neuroscience 2012, 208, 41-48). In a murine model of neuroinflammation, induction of LRRK2 in microglia was observed and inhibition of LRRK2 kinase activity with small molecule LRRK2 inhibitors (LRRK2-IN-1 or sunitinib) or LRRK2 knockout resulted in attenuation of TNF-α secretion and nitric oxide synthase (iNOS) induction (Moehle, M. et al. J. Neurosci. 2012, 32(5), 1602-1611). The most common of the LRRK2 mutations, G2019S, is present in more than 85% of PD patients carrying LRRK2 mutations. This mutation, which is present in the LRRK2 kinase domain, leads to an enhancement of LRRK2 kinase activity. In the human brain LRRK2 expression is highest in the same regions of the brain that are impacted by PD, and LRRK2 is found in Lewy Bodies, a hallmark of PD. Recent studies indicate that a potent, selective, brain-penetrant kinase inhibitor for LRRK2 could be a therapeutic treatment for PD.
Dementia results from a wide variety of distinctive pathological processes. The most common pathological processes causing dementia are AD, cerebral amyloid angiopathy (CM) and prion-mediated diseases (see, e.g., Haan et al., Clin. Neurol. Neurosurg. 1990, 92(4):305-310; Glenner et al., J. Neurol. Sci. 1989, 94:1-28). AD is a progressive, neurodegenerative disorder characterized by memory impairment and cognitive dysfunction. AD affects nearly half of all people past the age of 85, the most rapidly growing portion of the United States population. As such, the number of AD patients in the United States is expected to increase from about 4 million to about 14 million by 2050. LRRK2 mutations have been associated with AD-like pathology, which suggests that there may be a partial overlap between the neurodegenerative pathways in both AD and PD (Zimprach, A. et al. Neuron 2004, 44, 601-607). In addition, the LRRK2 R1628P variant (COR domain) has been associated with an increased incidence of AD in a certain population, perhaps resulting from increased apoptosis and cell death (Zhao, Y. et al.; Neurobiology of Aging 2011, 32, 1990-1993.
An increased incidence of certain non-skin cancers such as renal, breast, lung and prostate cancers, as well as acute myelogenous leukemia (AML), has been reported in Parkinson's disease patients with the LRRK2 G2019S mutation (Saunders-Pullman, R. et al.; Movement Disorders, 2010, 25(15), 2536-2541). Since the G2019S mutation is associated with increased LRRK2 kinase activity, inhibition of this activity may be useful in the treatment of cancer, such as kidney, breast, lung, prostate and blood cancers.
Inflammatory bowel disease (IBD) or Crohn's disease (CD) is a complex disease and is believed to result from an inappropriate immune response to microbiota in the intestinal tract. GWA studies have recently identified LRRK2 as a major susceptibility gene for Crohn's disease, particularly the M2397T polymorphism in the WD40 domain (Liu, Z. et al. Nat. Immunol. 2011, 12, 1063-1070). In a recent study LRRK2 deficient mice were found to be more susceptible to dextran sodium sulfate induced colitis than their wild-type counterparts, indicating that LRRK2 may play a role in the pathogenesis of IBD (Liu, Z. and Lenardo, M.; Cell Research 2012, 1-3).
Both non-selective and selective small molecule compounds with LRRK2 inhibitory activity such as staurosporine, sunitinib, LRRK2-IN-1, CZC-25146, TAE684 and those in WO 2011/141756, WO 2012/028629 and WO 2012/058193 have been described. It is desirable to provide compounds which are potent and selective inhibitors of LRRK2 with a favorable pharmacokinetic profile and the ability to traverse the blood brain barrier. Accordingly, the present invention is directed to novel 3,4-disubstituted-1H-pyrrolo[2,3-b]pyridine and 4,5-disubstituted-7H-pyrrolo[2,3-c]pyridazine compounds with LRRK2 inhibitory activity and the use of these compounds in the treatment of diseases associated with LRRK2, such as neurodegenerative diseases, including PD.